Field Service - Parts sold at 0 Quantity

Hello,

I have been getting word from our Service department that sometimes when a part is sold, the quantity is reduced to 0.  It does happen on most, it happens maybe once or twice a month, but has anyone else experienced this issue?

My understanding of the issue is they add the part, the quantity is at 1, they close out of the Parts window and the quantity is reduced to 0 sometime later when the call is modified.